/*----------------------------------------------------------------------------/
/ TJpgDec - Tiny JPEG Decompressor R0.01c                     (C)ChaN, 2019
/-----------------------------------------------------------------------------/
/ The TJpgDec is a generic JPEG decompressor module for tiny embedded systems.
/ This is a free software that opened for education, research and commercial
/  developments under license policy of following terms.
/
/  Copyright (C) 2019, ChaN, all right reserved.
/
/ * The TJpgDec module is a free software and there is NO WARRANTY.
/ * No restriction on use. You can use, modify and redistribute it for
/   personal, non-profit or commercial products UNDER YOUR RESPONSIBILITY.
/ * Redistributions of source code must retain the above copyright notice.
/
/-----------------------------------------------------------------------------/
/ Oct 04, 2011 R0.01  First release.
/ Feb 19, 2012 R0.01a Fixed decompression fails when scan starts with an escape
seq. / Sep 03, 2012 R0.01b Added JD_TBLCLIP option. / Mar 16, 2019 R0.01c
Supprted stdint.h.
/----------------------------------------------------------------------------*/

#include "tjpgd.h"

#include "config.h"

/*-----------------------------------------------*/
/* Zigzag-order to raster-order conversion table */
/*-----------------------------------------------*/

#define ZIG(n) Zig[n]

static const uint8_t Zig[64] =
    {/* Zigzag-order to raster-order conversion table */
     0,  1,  8,  16, 9,  2,  3,  10, 17, 24, 32, 25, 18, 11, 4,  5,
     12, 19, 26, 33, 40, 48, 41, 34, 27, 20, 13, 6,  7,  14, 21, 28,
     35, 42, 49, 56, 57, 50, 43, 36, 29, 22, 15, 23, 30, 37, 44, 51,
     58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62, 63};

/*-------------------------------------------------*/
/* Input scale factor of Arai algorithm            */
/* (scaled up 16 bits for fixed point operations)  */
/*-------------------------------------------------*/

#define IPSF(n) Ipsf[n]

static const uint16_t Ipsf[64] =
    {/* See also aa_idct.png */
     (uint16_t)(1.00000 * 8192), (uint16_t)(1.38704 * 8192),
     (uint16_t)(1.30656 * 8192), (uint16_t)(1.17588 * 8192),
     (uint16_t)(1.00000 * 8192), (uint16_t)(0.78570 * 8192),
     (uint16_t)(0.54120 * 8192), (uint16_t)(0.27590 * 8192),
     (uint16_t)(1.38704 * 8192), (uint16_t)(1.92388 * 8192),
     (uint16_t)(1.81226 * 8192), (uint16_t)(1.63099 * 8192),
     (uint16_t)(1.38704 * 8192), (uint16_t)(1.08979 * 8192),
     (uint16_t)(0.75066 * 8192), (uint16_t)(0.38268 * 8192),
     (uint16_t)(1.30656 * 8192), (uint16_t)(1.81226 * 8192),
     (uint16_t)(1.70711 * 8192), (uint16_t)(1.53636 * 8192),
     (uint16_t)(1.30656 * 8192), (uint16_t)(1.02656 * 8192),
     (uint16_t)(0.70711 * 8192), (uint16_t)(0.36048 * 8192),
     (uint16_t)(1.17588 * 8192), (uint16_t)(1.63099 * 8192),
     (uint16_t)(1.53636 * 8192), (uint16_t)(1.38268 * 8192),
     (uint16_t)(1.17588 * 8192), (uint16_t)(0.92388 * 8192),
     (uint16_t)(0.63638 * 8192), (uint16_t)(0.32442 * 8192),
     (uint16_t)(1.00000 * 8192), (uint16_t)(1.38704 * 8192),
     (uint16_t)(1.30656 * 8192), (uint16_t)(1.17588 * 8192),
     (uint16_t)(1.00000 * 8192), (uint16_t)(0.78570 * 8192),
     (uint16_t)(0.54120 * 8192), (uint16_t)(0.27590 * 8192),
     (uint16_t)(0.78570 * 8192), (uint16_t)(1.08979 * 8192),
     (uint16_t)(1.02656 * 8192), (uint16_t)(0.92388 * 8192),
     (uint16_t)(0.78570 * 8192), (uint16_t)(0.61732 * 8192),
     (uint16_t)(0.42522 * 8192), (uint16_t)(0.21677 * 8192),
     (uint16_t)(0.54120 * 8192), (uint16_t)(0.75066 * 8192),
     (uint16_t)(0.70711 * 8192), (uint16_t)(0.63638 * 8192),
     (uint16_t)(0.54120 * 8192), (uint16_t)(0.42522 * 8192),
     (uint16_t)(0.29290 * 8192), (uint16_t)(0.14932 * 8192),
     (uint16_t)(0.27590 * 8192), (uint16_t)(0.38268 * 8192),
     (uint16_t)(0.36048 * 8192), (uint16_t)(0.32442 * 8192),
     (uint16_t)(0.27590 * 8192), (uint16_t)(0.21678 * 8192),
     (uint16_t)(0.14932 * 8192), (uint16_t)(0.07612 * 8192)};

/*---------------------------------------------*/
/* Conversion table for fast clipping process  */
/*---------------------------------------------*/

#if JD_TBLCLIP

#define BYTECLIP(v) Clip8[(uint16_t)(v) & 0x3FF]

static const uint8_t Clip8[1024] = {
    /* 0..255 */
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
    21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
    40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58,
    59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77,
    78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
    97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,
    113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
    128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142,
    143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157,
    158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172,
    173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187,
    188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202,
    203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217,
    218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232,
    233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247,
    248, 249, 250, 251, 252, 253, 254, 255,
    /* 256..511 */
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255,
    /* -512..-257 */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0,
    /* -256..-1 */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0};

#else /* JD_TBLCLIP */

inline uint8_t BYTECLIP(int16_t val) {
  if (val < 0) val = 0;
  if (val > 255) val = 255;

  return (uint8_t)val;
}

#endif

/*-----------------------------------------------------------------------*/
/* Allocate a memory block from memory pool                              */
/*-----------------------------------------------------------------------*/

static void*
alloc_pool(/* Pointer to allocated memory block (NULL:no memory available) */
           JDEC* jd,   /* Pointer to the decompressor object */
           uint16_t nd /* Number of bytes to allocate */
) {
  char* rp = 0;

  nd = (nd + 3) & ~3; /* Align block size to the word boundary */

  if (jd->sz_pool >= nd) {
    jd->sz_pool -= nd;
    rp = (char*)jd->pool;        /* Get start of available memory pool */
    jd->pool = (void*)(rp + nd); /* Allocate requierd bytes */
  }

  return (
      void*)rp; /* Return allocated memory block (NULL:no memory to allocate) */
}

/*-----------------------------------------------------------------------*/
/* Create de-quantization and prescaling tables with a DQT segment       */
/*-----------------------------------------------------------------------*/

static int
create_qt_tbl(                     /* 0:OK, !0:Failed */
              JDEC* jd,            /* Pointer to the decompressor object */
              const uint8_t* data, /* Pointer to the quantizer tables */
              uint16_t ndata       /* Size of input data */
) {
  uint16_t i;
  uint8_t d, z;
  int32_t* pb;

  while (ndata) {                    /* Process all tables in the segment */
    if (ndata < 65) return JDR_FMT1; /* Err: table size is unaligned */
    ndata -= 65;
    d = *data++;                   /* Get table property */
    if (d & 0xF0) return JDR_FMT1; /* Err: not 8-bit resolution */
    i = d & 3;                     /* Get table ID */
    pb = alloc_pool(
        jd, 64 * sizeof(int32_t)); /* Allocate a memory block for the table */
    if (!pb) return JDR_MEM1;      /* Err: not enough memory */
    jd->qttbl[i] = pb;             /* Register the table */
    for (i = 0; i < 64; i++) {     /* Load the table */
      z = ZIG(i);                  /* Zigzag-order to raster-order conversion */
      pb[z] = (int32_t)((uint32_t)*data++ *
                        IPSF(z)); /* Apply scale factor of Arai algorithm to the
                                     de-quantizers */
    }
  }

  return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Create huffman code tables with a DHT segment                         */
/*-----------------------------------------------------------------------*/

static int create_huffman_tbl(          /* 0:OK, !0:Failed */
                              JDEC* jd, /* Pointer to the decompressor object */
                              const uint8_t* data, /* Pointer to the packed
                                                      huffman tables */
                              uint16_t ndata       /* Size of input data */
) {
  uint16_t i, j, b, np, cls, num;
  uint8_t d, *pb, *pd;
  uint16_t hc, *ph;

  while (ndata) {                    /* Process all tables in the segment */
    if (ndata < 17) return JDR_FMT1; /* Err: wrong data size */
    ndata -= 17;
    d = *data++;                   /* Get table number and class */
    if (d & 0xEE) return JDR_FMT1; /* Err: invalid class/number */
    cls = d >> 4;
    num = d & 0x0F; /* class = dc(0)/ac(1), table number = 0/1 */
    pb = alloc_pool(
        jd, 16); /* Allocate a memory block for the bit distribution table */
    if (!pb) return JDR_MEM1; /* Err: not enough memory */
    jd->huffbits[num][cls] = pb;
    for (np = i = 0; i < 16;
         i++) { /* Load number of patterns for 1 to 16-bit code */
      np += (pb[i] = *data++); /* Get sum of code words for each code */
    }
    ph = alloc_pool(
        jd, (uint16_t)(np * sizeof(uint16_t))); /* Allocate a memory block for
                                                   the code word table */
    if (!ph) return JDR_MEM1;                   /* Err: not enough memory */
    jd->huffcode[num][cls] = ph;
    hc = 0;
    for (j = i = 0; i < 16; i++) { /* Re-build huffman code word table */
      b = pb[i];
      while (b--) ph[j++] = hc++;
      hc <<= 1;
    }

    if (ndata < np) return JDR_FMT1; /* Err: wrong data size */
    ndata -= np;
    pd = alloc_pool(jd, np);  /* Allocate a memory block for the decoded data */
    if (!pd) return JDR_MEM1; /* Err: not enough memory */
    jd->huffdata[num][cls] = pd;
    for (i = 0; i < np;
         i++) { /* Load decoded data corresponds to each code ward */
      d = *data++;
      if (!cls && d > 11) return JDR_FMT1;
      *pd++ = d;
    }
  }

  return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Extract N bits from input stream                                      */
/*-----------------------------------------------------------------------*/

static int bitext(          /* >=0: extracted data, <0: error code */
                  JDEC* jd, /* Pointer to the decompressor object */
                  int nbit  /* Number of bits to extract (1 to 11) */
) {
  uint8_t msk, s, *dp;
  uint16_t dc, v, f;

  msk = jd->dmsk;
  dc = jd->dctr;
  dp = jd->dptr; /* Bit mask, number of data available, read ptr */
  s = *dp;
  v = f = 0;
  do {
    if (!msk) {         /* Next byte? */
      if (!dc) {        /* No input data is available, re-fill input buffer */
        dp = jd->inbuf; /* Top of input buffer */
        dc = jd->infunc(jd, dp, JD_SZBUF);
        if (!dc)
          return 0 -
                 (int16_t)
                     JDR_INP; /* Err: read error or wrong stream termination */
      } else {
        dp++; /* Next data ptr */
      }
      dc--;    /* Decrement number of available bytes */
      if (f) { /* In flag sequence? */
        f = 0; /* Exit flag sequence */
        if (*dp != 0)
          return 0 - (int16_t)JDR_FMT1; /* Err: unexpected flag is detected (may
                                           be collapted data) */
        *dp = s = 0xFF;                 /* The flag is a data 0xFF */
      } else {
        s = *dp;         /* Get next data byte */
        if (s == 0xFF) { /* Is start of flag sequence? */
          f = 1;
          continue; /* Enter flag sequence */
        }
      }
      msk = 0x80; /* Read from MSB */
    }
    v <<= 1; /* Get a bit */
    if (s & msk) v++;
    msk >>= 1;
    nbit--;
  } while (nbit);
  jd->dmsk = msk;
  jd->dctr = dc;
  jd->dptr = dp;

  return (int)v;
}

/*-----------------------------------------------------------------------*/
/* Extract a huffman decoded data from input stream                      */
/*-----------------------------------------------------------------------*/

static int16_t
huffext(                       /* >=0: decoded data, <0: error code */
        JDEC* jd,              /* Pointer to the decompressor object */
        const uint8_t* hbits,  /* Pointer to the bit distribution table */
        const uint16_t* hcode, /* Pointer to the code word table */
        const uint8_t* hdata   /* Pointer to the data table */
) {
  uint8_t msk, s, *dp;
  uint16_t dc, v, f, bl, nd;

  msk = jd->dmsk;
  dc = jd->dctr;
  dp = jd->dptr; /* Bit mask, number of data available, read ptr */
  s = *dp;
  v = f = 0;
  bl = 16; /* Max code length */
  do {
    if (!msk) {         /* Next byte? */
      if (!dc) {        /* No input data is available, re-fill input buffer */
        dp = jd->inbuf; /* Top of input buffer */
        dc = jd->infunc(jd, dp, JD_SZBUF);
        if (!dc)
          return 0 -
                 (int16_t)
                     JDR_INP; /* Err: read error or wrong stream termination */
      } else {
        dp++; /* Next data ptr */
      }
      dc--;    /* Decrement number of available bytes */
      if (f) { /* In flag sequence? */
        f = 0; /* Exit flag sequence */
        if (*dp != 0)
          return 0 - (int16_t)JDR_FMT1; /* Err: unexpected flag is detected (may
                                           be collapted data) */
        *dp = s = 0xFF;                 /* The flag is a data 0xFF */
      } else {
        s = *dp;         /* Get next data byte */
        if (s == 0xFF) { /* Is start of flag sequence? */
          f = 1;
          continue; /* Enter flag sequence, get trailing byte */
        }
      }
      msk = 0x80; /* Read from MSB */
    }
    v <<= 1; /* Get a bit */
    if (s & msk) v++;
    msk >>= 1;

    for (nd = *hbits++; nd;
         nd--) {           /* Search the code word in this bit length */
      if (v == *hcode++) { /* Matched? */
        jd->dmsk = msk;
        jd->dctr = dc;
        jd->dptr = dp;
        return *hdata; /* Return the decoded data */
      }
      hdata++;
    }
    bl--;
  } while (bl);

  return 0 -
         (int16_t)JDR_FMT1; /* Err: code not found (may be collapted data) */
}

/*-----------------------------------------------------------------------*/
/* Apply Inverse-DCT in Arai Algorithm (see also aa_idct.png)            */
/*-----------------------------------------------------------------------*/

static void block_idct(int32_t* src, /* Input block data (de-quantized and
                                        pre-scaled for Arai Algorithm) */
                       uint8_t* dst  /* Pointer to the destination to store the
                                        block as byte array */
) {
  const int32_t M13 = (int32_t)(1.41421 * 4096), M2 = (int32_t)(1.08239 * 4096),
                M4 = (int32_t)(2.61313 * 4096), M5 = (int32_t)(1.84776 * 4096);
  int32_t v0, v1, v2, v3, v4, v5, v6, v7;
  int32_t t10, t11, t12, t13;
  uint16_t i;

  /* Process columns */
  for (i = 0; i < 8; i++) {
    v0 = src[8 * 0]; /* Get even elements */
    v1 = src[8 * 2];
    v2 = src[8 * 4];
    v3 = src[8 * 6];

    t10 = v0 + v2; /* Process the even elements */
    t12 = v0 - v2;
    t11 = (v1 - v3) * M13 >> 12;
    v3 += v1;
    t11 -= v3;
    v0 = t10 + v3;
    v3 = t10 - v3;
    v1 = t11 + t12;
    v2 = t12 - t11;

    v4 = src[8 * 7]; /* Get odd elements */
    v5 = src[8 * 1];
    v6 = src[8 * 5];
    v7 = src[8 * 3];

    t10 = v5 - v4; /* Process the odd elements */
    t11 = v5 + v4;
    t12 = v6 - v7;
    v7 += v6;
    v5 = (t11 - v7) * M13 >> 12;
    v7 += t11;
    t13 = (t10 + t12) * M5 >> 12;
    v4 = t13 - (t10 * M2 >> 12);
    v6 = t13 - (t12 * M4 >> 12) - v7;
    v5 -= v6;
    v4 -= v5;

    src[8 * 0] = v0 + v7; /* Write-back transformed values */
    src[8 * 7] = v0 - v7;
    src[8 * 1] = v1 + v6;
    src[8 * 6] = v1 - v6;
    src[8 * 2] = v2 + v5;
    src[8 * 5] = v2 - v5;
    src[8 * 3] = v3 + v4;
    src[8 * 4] = v3 - v4;

    src++; /* Next column */
  }

  /* Process rows */
  src -= 8;
  for (i = 0; i < 8; i++) {
    v0 = src[0] +
         (128L << 8); /* Get even elements (remove DC offset (-128) here) */
    v1 = src[2];
    v2 = src[4];
    v3 = src[6];

    t10 = v0 + v2; /* Process the even elements */
    t12 = v0 - v2;
    t11 = (v1 - v3) * M13 >> 12;
    v3 += v1;
    t11 -= v3;
    v0 = t10 + v3;
    v3 = t10 - v3;
    v1 = t11 + t12;
    v2 = t12 - t11;

    v4 = src[7]; /* Get odd elements */
    v5 = src[1];
    v6 = src[5];
    v7 = src[3];

    t10 = v5 - v4; /* Process the odd elements */
    t11 = v5 + v4;
    t12 = v6 - v7;
    v7 += v6;
    v5 = (t11 - v7) * M13 >> 12;
    v7 += t11;
    t13 = (t10 + t12) * M5 >> 12;
    v4 = t13 - (t10 * M2 >> 12);
    v6 = t13 - (t12 * M4 >> 12) - v7;
    v5 -= v6;
    v4 -= v5;

    dst[0] = BYTECLIP((v0 + v7) >>
                      8); /* Descale the transformed values 8 bits and output */
    dst[7] = BYTECLIP((v0 - v7) >> 8);
    dst[1] = BYTECLIP((v1 + v6) >> 8);
    dst[6] = BYTECLIP((v1 - v6) >> 8);
    dst[2] = BYTECLIP((v2 + v5) >> 8);
    dst[5] = BYTECLIP((v2 - v5) >> 8);
    dst[3] = BYTECLIP((v3 + v4) >> 8);
    dst[4] = BYTECLIP((v3 - v4) >> 8);
    dst += 8;

    src += 8; /* Next row */
  }
}

/*-----------------------------------------------------------------------*/
/* Load all blocks in the MCU into working buffer                        */
/*-----------------------------------------------------------------------*/

static JRESULT mcu_load(JDEC* jd /* Pointer to the decompressor object */
) {
  int32_t* tmp =
      (int32_t*)jd->workbuf; /* Block working buffer for de-quantize and IDCT */
  int b, d, e;
  uint16_t blk, nby, nbc, i, z, id, cmp;
  uint8_t* bp;
  const uint8_t *hb, *hd;
  const uint16_t* hc;
  const int32_t* dqf;

  nby = jd->msx * jd->msy; /* Number of Y blocks (1, 2 or 4) */
  nbc = 2;                 /* Number of C blocks (2) */
  bp = jd->mcubuf;         /* Pointer to the first block */

  for (blk = 0; blk < nby + nbc; blk++) {
    cmp =
        (blk < nby) ? 0 : blk - nby + 1; /* Component number 0:Y, 1:Cb, 2:Cr */
    id = cmp ? 1 : 0;                    /* Huffman table ID of the component */

    /* Extract a DC element from input stream */
    hb = jd->huffbits[id][0]; /* Huffman table for the DC element */
    hc = jd->huffcode[id][0];
    hd = jd->huffdata[id][0];
    b = huffext(jd, hb, hc, hd); /* Extract a huffman coded data (bit length) */
    if (b < 0) return 0 - b;     /* Err: invalid code or input */
    d = jd->dcv[cmp];            /* DC value of previous block */
    if (b) {             /* If there is any difference from previous block */
      e = bitext(jd, b); /* Extract data bits */
      if (e < 0) return 0 - e;         /* Err: input */
      b = 1 << (b - 1);                /* MSB position */
      if (!(e & b)) e -= (b << 1) - 1; /* Restore sign if needed */
      d += e;                          /* Get current value */
      jd->dcv[cmp] = (int16_t)d; /* Save current DC value for next block */
    }
    dqf =
        jd->qttbl[jd->qtid[cmp]]; /* De-quantizer table ID for this component */
    tmp[0] = d * dqf[0] >> 8;     /* De-quantize, apply scale factor of Arai
                                     algorithm and descale 8 bits */

    /* Extract following 63 AC elements from input stream */
    for (i = 1; i < 64; tmp[i++] = 0)
      ;                       /* Clear rest of elements */
    hb = jd->huffbits[id][1]; /* Huffman table for the AC elements */
    hc = jd->huffcode[id][1];
    hd = jd->huffdata[id][1];
    i = 1; /* Top of the AC elements */
    do {
      b = huffext(
          jd, hb, hc,
          hd); /* Extract a huffman coded value (zero runs and bit length) */
      if (b == 0) break;       /* EOB? */
      if (b < 0) return 0 - b; /* Err: invalid code or input error */
      z = (uint16_t)b >> 4;    /* Number of leading zero elements */
      if (z) {
        i += z;                       /* Skip zero elements */
        if (i >= 64) return JDR_FMT1; /* Too long zero run */
      }
      if (b &= 0x0F) {                   /* Bit length */
        d = bitext(jd, b);               /* Extract data bits */
        if (d < 0) return 0 - d;         /* Err: input device */
        b = 1 << (b - 1);                /* MSB position */
        if (!(d & b)) d -= (b << 1) - 1; /* Restore negative value if needed */
        z = ZIG(i); /* Zigzag-order to raster-order converted index */
        tmp[z] = d * dqf[z] >> 8; /* De-quantize, apply scale factor of Arai
                                     algorithm and descale 8 bits */
      }
    } while (++i < 64); /* Next AC element */

    if (JD_USE_SCALE && jd->scale == 3) {
      *bp = (uint8_t)((*tmp / 256) +
                      128); /* If scale ratio is 1/8, IDCT can be ommited and
                               only DC element is used */
    } else {
      block_idct(tmp,
                 bp); /* Apply IDCT and store the block to the MCU buffer */
    }

    bp += 64; /* Next block */
  }

  return JDR_OK; /* All blocks have been loaded successfully */
}

/*-----------------------------------------------------------------------*/
/* Output an MCU: Convert YCrCb to RGB and output it in RGB form         */
/*-----------------------------------------------------------------------*/

static JRESULT mcu_output(
    JDEC* jd, /* Pointer to the decompressor object */
    uint16_t (*outfunc)(JDEC*, void*, JRECT*), /* RGB output function */
    uint16_t x, /* MCU position in the image (left of the MCU) */
    uint16_t y  /* MCU position in the image (top of the MCU) */
) {
  const int16_t CVACC = (sizeof(int16_t) > 2) ? 1024 : 128;
  uint16_t ix, iy, mx, my, rx, ry;
  int16_t yy, cb, cr;
  uint8_t *py, *pc, *rgb24;
  JRECT rect;

  mx = jd->msx * 8;
  my = jd->msy * 8; /* MCU size (pixel) */
  rx = (x + mx <= jd->width)
           ? mx
           : jd->width - x; /* Output rectangular size (it may be clipped at
                               right/bottom end) */
  ry = (y + my <= jd->height) ? my : jd->height - y;
  if (JD_USE_SCALE) {
    rx >>= jd->scale;
    ry >>= jd->scale;
    if (!rx || !ry)
      return JDR_OK; /* Skip this MCU if all pixel is to be rounded off */
    x >>= jd->scale;
    y >>= jd->scale;
  }
  rect.left = x;
  rect.right = x + rx - 1; /* Rectangular area in the frame buffer */
  rect.top = y;
  rect.bottom = y + ry - 1;

  if (!JD_USE_SCALE || jd->scale != 3) { /* Not for 1/8 scaling */

    /* Build an RGB MCU from discrete comopnents */
    rgb24 = (uint8_t*)jd->workbuf;
    for (iy = 0; iy < my; iy++) {
      pc = jd->mcubuf;
      py = pc + iy * 8;
      if (my == 16) { /* Double block height? */
        pc += 64 * 4 + (iy >> 1) * 8;
        if (iy >= 8) py += 64;
      } else { /* Single block height */
        pc += mx * 8 + iy * 8;
      }
      for (ix = 0; ix < mx; ix++) {
        cb = pc[0] - 128; /* Get Cb/Cr component and restore right level */
        cr = pc[64] - 128;
        if (mx == 16) { /* Double block width? */
          if (ix == 8)
            py += 64 - 8; /* Jump to next block if double block heigt */
          pc += ix & 1;   /* Increase chroma pointer every two pixels */
        } else {          /* Single block width */
          pc++;           /* Increase chroma pointer every pixel */
        }
        yy = *py++; /* Get Y component */

        /* Convert YCbCr to RGB */
        *rgb24++ =
            /* R */ BYTECLIP(yy + ((int16_t)(1.402 * CVACC) * cr) / CVACC);
        *rgb24++ = /* G */ BYTECLIP(yy - ((int16_t)(0.344 * CVACC) * cb +
                                          (int16_t)(0.714 * CVACC) * cr) /
                                             CVACC);
        *rgb24++ =
            /* B */ BYTECLIP(yy + ((int16_t)(1.772 * CVACC) * cb) / CVACC);
      }
    }

    /* Descale the MCU rectangular if needed */
    if (JD_USE_SCALE && jd->scale) {
      uint16_t x, y, r, g, b, s, w, a;
      uint8_t* op;

      /* Get averaged RGB value of each square correcponds to a pixel */
      s = jd->scale * 2;  /* Bumber of shifts for averaging */
      w = 1 << jd->scale; /* Width of square */
      a = (mx - w) * 3;   /* Bytes to skip for next line in the square */
      op = (uint8_t*)jd->workbuf;
      for (iy = 0; iy < my; iy += w) {
        for (ix = 0; ix < mx; ix += w) {
          rgb24 = (uint8_t*)jd->workbuf + (iy * mx + ix) * 3;
          r = g = b = 0;
          for (y = 0; y < w; y++) { /* Accumulate RGB value in the square */
            for (x = 0; x < w; x++) {
              r += *rgb24++;
              g += *rgb24++;
              b += *rgb24++;
            }
            rgb24 += a;
          } /* Put the averaged RGB value as a pixel */
          *op++ = (uint8_t)(r >> s);
          *op++ = (uint8_t)(g >> s);
          *op++ = (uint8_t)(b >> s);
        }
      }
    }

  } else { /* For only 1/8 scaling (left-top pixel in each block are the DC
              value of the block) */

    /* Build a 1/8 descaled RGB MCU from discrete comopnents */
    rgb24 = (uint8_t*)jd->workbuf;
    pc = jd->mcubuf + mx * my;
    cb = pc[0] - 128; /* Get Cb/Cr component and restore right level */
    cr = pc[64] - 128;
    for (iy = 0; iy < my; iy += 8) {
      py = jd->mcubuf;
      if (iy == 8) py += 64 * 2;
      for (ix = 0; ix < mx; ix += 8) {
        yy = *py; /* Get Y component */
        py += 64;

        /* Convert YCbCr to RGB */
        *rgb24++ =
            /* R */ BYTECLIP(yy + ((int16_t)(1.402 * CVACC) * cr / CVACC));
        *rgb24++ = /* G */ BYTECLIP(yy - ((int16_t)(0.344 * CVACC) * cb +
                                          (int16_t)(0.714 * CVACC) * cr) /
                                             CVACC);
        *rgb24++ =
            /* B */ BYTECLIP(yy + ((int16_t)(1.772 * CVACC) * cb / CVACC));
      }
    }
  }

  /* Squeeze up pixel table if a part of MCU is to be truncated */
  mx >>= jd->scale;
  if (rx < mx) {
    uint8_t *s, *d;
    uint16_t x, y;

    s = d = (uint8_t*)jd->workbuf;
    for (y = 0; y < ry; y++) {
      for (x = 0; x < rx; x++) { /* Copy effective pixels */
        *d++ = *s++;
        *d++ = *s++;
        *d++ = *s++;
      }
      s += (mx - rx) * 3; /* Skip truncated pixels */
    }
  }

  /* Convert RGB888 to RGB565 if needed */
  if (JD_FORMAT == 1) {
    uint8_t* s = (uint8_t*)jd->workbuf;
    uint16_t w, *d = (uint16_t*)s;
    uint16_t n = rx * ry;

    do {
      w = (*s++ & 0xF8) << 8;  /* RRRRR----------- */
      w |= (*s++ & 0xFC) << 3; /* -----GGGGGG----- */
      w |= *s++ >> 3;          /* -----------BBBBB */
#ifdef TJPGD_NEEDS_BYTESWAP
      *d++ = (w >> 8) | (w << 8);
#else
      *d++ = w;
#endif
    } while (--n);
  }

  /* Output the RGB rectangular */
  return outfunc(jd, jd->workbuf, &rect) ? JDR_OK : JDR_INTR;
}

/*-----------------------------------------------------------------------*/
/* Process restart interval                                              */
/*-----------------------------------------------------------------------*/

static JRESULT restart(JDEC* jd,     /* Pointer to the decompressor object */
                       uint16_t rstn /* Expected restert sequense number */
) {
  uint16_t i, dc;
  uint16_t d;
  uint8_t* dp;

  /* Discard padding bits and get two bytes from the input stream */
  dp = jd->dptr;
  dc = jd->dctr;
  d = 0;
  for (i = 0; i < 2; i++) {
    if (!dc) { /* No input data is available, re-fill input buffer */
      dp = jd->inbuf;
      dc = jd->infunc(jd, dp, JD_SZBUF);
      if (!dc) return JDR_INP;
    } else {
      dp++;
    }
    dc--;
    d = (d << 8) | *dp; /* Get a byte */
  }
  jd->dptr = dp;
  jd->dctr = dc;
  jd->dmsk = 0;

  /* Check the marker */
  if ((d & 0xFFD8) != 0xFFD0 || (d & 7) != (rstn & 7)) {
    return JDR_FMT1; /* Err: expected RSTn marker is not detected (may be
                        collapted data) */
  }

  /* Reset DC offset */
  jd->dcv[2] = jd->dcv[1] = jd->dcv[0] = 0;

  return JDR_OK;
}

/*-----------------------------------------------------------------------*/
/* Analyze the JPEG image and Initialize decompressor object             */
/*-----------------------------------------------------------------------*/

#define LDB_WORD(ptr)                                \
  (uint16_t)(((uint16_t) * ((uint8_t*)(ptr)) << 8) | \
             (uint16_t) * (uint8_t*)((ptr) + 1))

JRESULT jd_prepare(
    JDEC* jd, /* Blank decompressor object */
    uint16_t (*infunc)(JDEC*, uint8_t*,
                       uint16_t), /* JPEG strem input function */
    void* pool,       /* Working buffer for the decompression session */
    uint16_t sz_pool, /* Size of working buffer */
    void* dev         /* I/O device identifier for the session */
) {
  uint8_t *seg, b;
  uint16_t marker;
  uint32_t ofs;
  uint16_t n, i, j, len;
  JRESULT rc;

  if (!pool) return JDR_PAR;

  jd->pool = pool;       /* Work memroy */
  jd->sz_pool = sz_pool; /* Size of given work memory */
  jd->infunc = infunc;   /* Stream input function */
  jd->device = dev;      /* I/O device identifier */
  jd->nrst = 0;          /* No restart interval (default) */

  for (i = 0; i < 2; i++) { /* Nulls pointers */
    for (j = 0; j < 2; j++) {
      jd->huffbits[i][j] = 0;
      jd->huffcode[i][j] = 0;
      jd->huffdata[i][j] = 0;
    }
  }
  for (i = 0; i < 4; jd->qttbl[i++] = 0)
    ;

  jd->inbuf = seg = alloc_pool(jd, JD_SZBUF); /* Allocate stream input buffer */
  if (!seg) return JDR_MEM1;

  if (jd->infunc(jd, seg, 2) != 2) return JDR_INP; /* Check SOI marker */
  if (LDB_WORD(seg) != 0xFFD8) return JDR_FMT1; /* Err: SOI is not detected */
  ofs = 2;

  for (;;) {
    /* Get a JPEG marker */
    if (jd->infunc(jd, seg, 4) != 4) return JDR_INP;
    marker = LDB_WORD(seg);  /* Marker */
    len = LDB_WORD(seg + 2); /* Length field */
    if (len <= 2 || (marker >> 8) != 0xFF) return JDR_FMT1;
    len -= 2;       /* Content size excluding length field */
    ofs += 4 + len; /* Number of bytes loaded */

    switch (marker & 0xFF) {
      case 0xC0: /* SOF0 (baseline JPEG) */
        /* Load segment data */
        if (len > JD_SZBUF) return JDR_MEM2;
        if (jd->infunc(jd, seg, len) != len) return JDR_INP;

        jd->width = LDB_WORD(seg + 3);  /* Image width in unit of pixel */
        jd->height = LDB_WORD(seg + 1); /* Image height in unit of pixel */
        if (seg[5] != 3)
          return JDR_FMT3; /* Err: Supports only Y/Cb/Cr format */

        /* Check three image components */
        for (i = 0; i < 3; i++) {
          b = seg[7 + 3 * i]; /* Get sampling factor */
          if (!i) {           /* Y component */
            if (b != 0x11 && b != 0x22 &&
                b != 0x21) {   /* Check sampling factor */
              return JDR_FMT3; /* Err: Supports only 4:4:4, 4:2:0 or 4:2:2 */
            }
            jd->msx = b >> 4;
            jd->msy = b & 15; /* Size of MCU [blocks] */
          } else {            /* Cb/Cr component */
            if (b != 0x11)
              return JDR_FMT3; /* Err: Sampling factor of Cr/Cb must be 1 */
          }
          b = seg[8 + 3 * i]; /* Get dequantizer table ID for this component */
          if (b > 3) return JDR_FMT3; /* Err: Invalid ID */
          jd->qtid[i] = b;
        }
        break;

      case 0xDD: /* DRI */
        /* Load segment data */
        if (len > JD_SZBUF) return JDR_MEM2;
        if (jd->infunc(jd, seg, len) != len) return JDR_INP;

        /* Get restart interval (MCUs) */
        jd->nrst = LDB_WORD(seg);
        break;

      case 0xC4: /* DHT */
        /* Load segment data */
        if (len > JD_SZBUF) return JDR_MEM2;
        if (jd->infunc(jd, seg, len) != len) return JDR_INP;

        /* Create huffman tables */
        rc = create_huffman_tbl(jd, seg, len);
        if (rc) return rc;
        break;

      case 0xDB: /* DQT */
        /* Load segment data */
        if (len > JD_SZBUF) return JDR_MEM2;
        if (jd->infunc(jd, seg, len) != len) return JDR_INP;

        /* Create de-quantizer tables */
        rc = create_qt_tbl(jd, seg, len);
        if (rc) return rc;
        break;

      case 0xDA: /* SOS */
        /* Load segment data */
        if (len > JD_SZBUF) return JDR_MEM2;
        if (jd->infunc(jd, seg, len) != len) return JDR_INP;

        if (!jd->width || !jd->height)
          return JDR_FMT1; /* Err: Invalid image size */

        if (seg[0] != 3)
          return JDR_FMT3; /* Err: Supports only three color components format
                            */

        /* Check if all tables corresponding to each components have been loaded
         */
        for (i = 0; i < 3; i++) {
          b = seg[2 + 2 * i]; /* Get huffman table ID */
          if (b != 0x00 && b != 0x11)
            return JDR_FMT3; /* Err: Different table number for DC/AC element */
          b = i ? 1 : 0;
          if (!jd->huffbits[b][0] ||
              !jd->huffbits[b][1]) { /* Check dc/ac huffman table for this
                                        component */
            return JDR_FMT1;         /* Err: Nnot loaded */
          }
          if (!jd->qttbl[jd->qtid[i]]) { /* Check dequantizer table for this
                                            component */
            return JDR_FMT1;             /* Err: Not loaded */
          }
        }

        /* Allocate working buffer for MCU and RGB */
        n = jd->msy * jd->msx;   /* Number of Y blocks in the MCU */
        if (!n) return JDR_FMT1; /* Err: SOF0 has not been loaded */
        len = n * 64 * 2 + 64;   /* Allocate buffer for IDCT and RGB output */
        if (len < 256)
          len = 256; /* but at least 256 byte is required for IDCT */
        jd->workbuf =
            alloc_pool(jd, len); /* and it may occupy a part of following MCU
                                    working buffer for RGB output */
        if (!jd->workbuf) return JDR_MEM1; /* Err: not enough memory */
        jd->mcubuf = (uint8_t*)alloc_pool(
            jd, (uint16_t)((n + 2) * 64)); /* Allocate MCU working buffer */
        if (!jd->mcubuf) return JDR_MEM1;  /* Err: not enough memory */

        /* Pre-load the JPEG data to extract it from the bit stream */
        jd->dptr = seg;
        jd->dctr = 0;
        jd->dmsk = 0;          /* Prepare to read bit stream */
        if (ofs %= JD_SZBUF) { /* Align read offset to JD_SZBUF */
          jd->dctr = jd->infunc(jd, seg + ofs, (uint16_t)(JD_SZBUF - ofs));
          jd->dptr = seg + ofs - 1;
        }

        return JDR_OK; /* Initialization succeeded. Ready to decompress the JPEG
                          image. */

      case 0xC1:         /* SOF1 */
      case 0xC2:         /* SOF2 */
      case 0xC3:         /* SOF3 */
      case 0xC5:         /* SOF5 */
      case 0xC6:         /* SOF6 */
      case 0xC7:         /* SOF7 */
      case 0xC9:         /* SOF9 */
      case 0xCA:         /* SOF10 */
      case 0xCB:         /* SOF11 */
      case 0xCD:         /* SOF13 */
      case 0xCE:         /* SOF14 */
      case 0xCF:         /* SOF15 */
      case 0xD9:         /* EOI */
        return JDR_FMT3; /* Unsuppoted JPEG standard (may be progressive JPEG)
                          */

      default: /* Unknown segment (comment, exif or etc..) */
        /* Skip segment data */
        if (jd->infunc(jd, 0, len) !=
            len) { /* Null pointer specifies to skip bytes of stream */
          return JDR_INP;
        }
    }
  }
}

/*-----------------------------------------------------------------------*/
/* Start to decompress the JPEG picture                                  */
/*-----------------------------------------------------------------------*/

JRESULT jd_decomp(JDEC* jd, /* Initialized decompression object */
                  uint16_t (*outfunc)(JDEC*, void*,
                                      JRECT*), /* RGB output function */
                  uint8_t scale /* Output de-scaling factor (0 to 3) */
) {
  uint16_t x, y, mx, my;
  uint16_t rst, rsc;
  JRESULT rc;

  if (scale > (JD_USE_SCALE ? 3 : 0)) return JDR_PAR;
  jd->scale = scale;

  mx = jd->msx * 8;
  my = jd->msy * 8; /* Size of the MCU (pixel) */

  jd->dcv[2] = jd->dcv[1] = jd->dcv[0] = 0; /* Initialize DC values */
  rst = rsc = 0;

  rc = JDR_OK;
  for (y = 0; y < jd->height; y += my) {  /* Vertical loop of MCUs */
    for (x = 0; x < jd->width; x += mx) { /* Horizontal loop of MCUs */
      if (jd->nrst &&
          rst++ == jd->nrst) { /* Process restart interval if enabled */
        rc = restart(jd, rsc++);
        if (rc != JDR_OK) return rc;
        rst = 1;
      }
      rc = mcu_load(jd); /* Load an MCU (decompress huffman coded stream and
                            apply IDCT) */
      if (rc != JDR_OK) return rc;
      rc = mcu_output(
          jd, outfunc, x,
          y); /* Output the MCU (color space conversion, scaling and output) */
      if (rc != JDR_OK) return rc;
    }
  }

  return rc;
}
